Vane pump



9 TOURU NAKAGAWA 3,549,237

' VANE PUMP Filed April 30, 1969 FIG./

INVENTOR T0141? NAKAGAWA United States Patent O 3,549,287 VANE PUMP Touru Nakagawa, Hitachi-shi, Japan, assignor to Hitachi, Ltd., Chiyoda-ku, Tokyo, Japan Filed Apr. 30, 1969, Ser. No. 820,479 Claims priority, application Japan, May 4, 1968, 43/316,022 Int. Cl. F04c 17/00, 27/00; F01c 19/00 US. Cl. 418-107 3 Claims ABSTRACT OF THE DISCLOSURE The invention discloses the improvement of a vane pump and particularly a vane pump of the type for use in sup plying air to a portion just behind an exhaust valve of an internal-combustion engine of an automobile thereby reburning unburnt gas. A rotor whose axis of rotation is eccentric relative to the axis of a housing in which is disposed said rotor, is so formed that the diameter of it is gradually reduced from the end of said rotor to which is applied the driving force toward the opposite end thereof, whereby the contact of the peripheral surface of said rotor with the inner surface of the housing, that is a stripper land thereof during high speed rotation can be prevented without materially decreasing the resistance to air leakage.

BACKGROUND OF THE INVENTION The present invention relates to a vane pump for example for use is supplying air to a portion just behind an exhaust valve of an automobile engine thereby reburning unburnt gas.

Not only in a vane pump but also in other types of pumps the leakage in the pump must be minimized in order to increase the volumetric efliciency of the pump. For this purpose, air leakage from the high pressure side into the lower pressure side in a pump must be minimized. Especially the clearance between a rotor and a housing stripper land, which is disposed between an inlet chamber and a discharge chamber of a pump, greatly influences the volumetric efliciency of the pump. This stripper land is a portion at which the rotary member of the pump is contiguous to its stationary member so that the stripper land must be spaced apart from the rotor by a suitable distance. Especially in case of a rotor having slots formed axially thereof, the end of the rotor opposite to the end to which is applied the driving force tends to displace radially at the higher speeds so that the rotor tends to contact with the housing.

SUMMARY OF THE INVENTION It is therefore the primary object of the present invention to provide the improvement of a vane pump by which a rotor can be positively prevented from contacting with a housing.

The present invention is best suited for a vane pump of the type comprising a housing having a cylindrical inner surface, a hollow cylindrical rotor rotatably disposed within said housing about an axis eccentrically of the axis of said housing with a substantially sealing engagement with one portion of the inner surface of said housing, a vane shaft extending in coaxial relation with said housing into the cavity of said hollow rotor, slots formed in said rotor and extended axially thereof, vanes each of which is carried by said vane shaft and extends through said slot toward the inner surface of said housing with the tip of said vane being in sealing relation with said inner surface of said housing and means for sealing a space between said vane and said rotor in said slot, whereby upon rotation of said rotor, said vanes are rotated about said vane shaft so that the revolving pumping spaces defined by the inner 3,549,287 Patented Dec. 22, 1970 surface of said housing, the peripheral surface of said rotor and said vane expand and contract so as to suck and discharge fluid.

The feature of the improvement of the present invention which is believed to be characteristic of the present invention resides in the fact that a clearance between the peripheral surface of said rotor and said one portion of said inner surface of said housing is enlarged or diverged gradually from the driving end of said rotor toward the end opposite to said driving end.

According to one aspect of the present invention, the View taken along the line 11-11 of FIG. 1 and FIG. outer diameter of said rotor is reduced gradually from said driving end toward said opposite end.

According to another aspect of the present invention, the clearance between the peripheral surface of said rotor and said one portion of said inner surface of said housing is diverged with an angle between 30' and 2.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings in which: FIG. 1 is a longitudinal sectional view of one embodiment of the vane pump according to the present invention; FIG. 2 is a sectional view taken along the line II-II' of FIG. 1 and FIG. 3 is an enlarged longitudinal sectional view illustrating the essential portion of the bottom of the housing relative to a rotor of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A housing 1 has a cylindrical inner wall 2 whose center is designated by reference character 0 and an end wall 3. An end bracket 4 has an end wall 5 in opposed relation with the end wall 3. A hollow rotor 6 rotates about the center 0 which is positioned eccentrically of the center 0 The driving shaft 7 of the rotor 6 has a pulley 13 fixed thereto and a rotary ring 8 is attached by screws 9 to the end of the rotor 6 opposite to the shaft 7. Into the rotary ring 8 is press-fitted a roller bearing 10 which is mounted on a boss portion 11 formed so as to extend inwardly from the end bracket 4. A ball bearing 12 is press-fitted into the housing 1 for receiving the shaft 7. Both of the boss portion 11 and the ball bearing 12 are coaxial with each other and with respect to the center 0 so that the rotor is rotated about the center 0 through the pulley 13. Vanes 14 are carried by a needle bearing 15 which in turn is carried by a vane shaft 16 one end of which is press-fitted into the boss portion 11 of the end bracket 4. The axis of the vane shaft 16 coincides with the center 0 of the housing inner wall and the vanes 14 rotate about the vane shaft 16.

The rotor 6 is provided with longitudinal slots 17 through which extend the vanes 14 toward the inner Wall of the housing. In order to prevent the air from leaking into the inside of the rotor 6, two bar-shaped carbons 18 are fitted into the slot 17 so that the vane 14 may be interposed therebetween. Between a suction port 19 and a discharge port 20 is formed a stripper land 21 with a predetermined clearance relative to the rotor 6.

The mode of the operation of the pump having the construction as described above will be described hereinafter. The rotor 6 is rotated through the pulley driven by suitable drive means not shown so that the vanes 14 are also rotated. The air is sucked through the inlet port 19 and then discharged through the discharge port 20. In this case, when the rotor 6 is rotated at high speed, the rotor 6 is displaced in radial direction thereof on the side opposite to the pulley because the longitudinal slots 17 are formed in the rotor 6, so that it is required to enlarge the clearance between the stripper land 21 and the rotor 6 at a sacrifice of volumetric efficiency in order to prevent the contact therebetween.

However, according to the present invention this contact between the rotor 6 and the stripper land 21 can be eliminated without a sacrifice of volumetric efliciency. That is, as shown in FIG. 3 the rotor 6 is tapered in such a manner that the clearance between the rotor 6 and the stripper land 21 diverges toward thecnd bracket with an angle between 30 and 2. In other words, the clearance on the side of the rotary ring 8 that is on the side opposite to the pulley is larger than that on the side of the pulley, whereby the contact of the rotor 6twith the stripper land 21 during high speed rotation of the rotor can be effectively prevented without reducing volumetric efiiciency. When the angle of divergence is in excess of 2, too much air leaks so that the vane pump cannot be used in practice. The above range of angle of divergence 6 was obtained based upon the results of extensive studies and experiments, and the optimum angleis approximately 1 that is between 50' and 120. The lowermost limit is 30' but this is due to errors in machining the rotor 6 so as to give a taper thereto. It is impossible in practice to give the angle of divergence 0 less than 30' as the clearance between oneportion of the inner surface of the housing and the peripheral surface of the rotor.

The present invention has been described so far with particular reference to the preferred embodim entthereof, but it will be understood that variations and modifications can be effected without departing the true spirit ofthet present invention'as described hereinabove and as defined in the appended claims.

What is claimed is: Y i

1, In a vane pump of the type comprising a housing having a cylindrical inner surface, 'a hollow cylindrical rotor rotatably disposed within said housing about an axis socentn'cally ofthe axisof said housing with a substantially sealing engagement with one portion of the inner surface of said housing, a vane shaft extending in coaxial rela tion with said housing into the cavity of saidhollow 4 rotor, slots formed in said rotor and extended axially thereof, vanes each of which is carried by said vane shaft and extends through said slot toward the inner surface of said housing with the tip of said vane being in sealing relation with said inner surface of said housing and means for sealing a space between said vane and said rotor in said slot, whereby upon rotation of said rotor, said vanes are rotated about said vane shaft so that the revolving pumping spaces defined by the inner surface of said housing, the peripheral surface of said rotor and said vane expand and contract so as to suck and discharge fluid, the improvement comprising said rotor and housing a clearance between the peripheral surface of the former and said one portion of the inner surface of the latter, said clearance diverged gradually from the driving end of said rotor toward the end opposite to said driving end.

' 2. A vane pump according to claim 1, wherein the outer diameter of said rotor is gradually reduced from said driving end toward said opposite end.

3. A vane pump according to claim 1, wherein said clearance between the peripheral surface of said rotor and said one portion of said inner surface of said housing is diverged with an angle between 30' and 2.

References Cited M. NEWMAN, Primary Examiner W. I. KRAUSS, Assistant Examiner US Cl. X.-R. 418174, 

